From: Andy Soos, ENN
Published June 9, 2010 12:51 PM

Down Deep in the Gulf of Mexico

By now most know about the oil gushing out in the Gulf of Mexico. Certainly it is floating on the surface but what is the effect underwater? One way is to measure the relative concentrations of PAHs (Polycyclic aromatic hydrocarbons). National Oceanic and Atmospheric Administration's (NOAA) independent analysis of water samples collected during the May 22-28 research mission of the University of South Florida’s R/V Weatherbird II confirmed the presence of very low concentrations of subsurface oil and PAHs (polycyclic aromatic hydrocarbons) at sampling depths ranging from 50 meters to 1,400 meters.

The Weatherbird II samples came from three stations: 40 and 42 nautical miles to the northeast of the well head and 142 nautical miles southeast of the well head. NOAA’s analysis of the presence of subsurface oil determined that the concentration of hydrocarbons is in the range of less than 0.5 parts per million, and PAH levels in range of parts per trillion.

Hydrocarbons (sometimes described as petroleum hydrocarbons or PHC)and PAHs are general indicators of the presence of a oil release.

PAHs are a group of compounds with fused aromatic of benzene rings such as anthracene which is composed of three fused benzene rings. Several members of this group are known or suspected carcinogens.

Such sampling can only be considered preliminary or interim pending further sampling and analysis.

Along with its analysis for the presence of oil and PAHs, NOAA’s tests to “fingerprint” the Weatherbird II oil samples to the BP oil spill source concluded that:

* Hydrocarbons found in surface samples taken at the Slick 1 source, 40 nautical miles northeast from the well head, were consistent with the BP oil spill source.

* Hydrocarbons found elsewhere could not be positively identified with the BP oil release primarily because the concentrations were so low.

Just because PAHs are detected at low levels, it does not mean they are derived from the current oil release, past releases or some sort of natural level.

“We have always known there is oil under the surface; the questions we are exploring are where is it, in what concentrations, where is it going, and what are the consequences for the health of the marine environment.  This research from the University of South Florida contributes to this larger, three dimensional puzzle we are trying to solve, in partnership with academic and NOAA scientists.” said NOAA Administrator Dr. Jane Lubchenco.

"NOAA’s analysis of the Weatherbird II samples shows that concentrations of hydrocarbons decrease with depth, with a notable exception of samples at 300 meters from Station 07, which warrants additional research attention," said Dr. Steven Murawski, chief scientists for NOAA Fisheries. “Also, PAH levels are very low in all samples, with only five of 25 having reportable concentrations of the priority pollutant PAHs.”

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